This application makes reference to, incorporates the same herein, and claims all benefits accruing under 35 U.S.C. xc2xa7119 from my application APPARATUS FOR BACK LIGHTING OF LCD HAVING AN OPTICAL FIBER filed with the Korean Industrial Property Office on Feb. 21, 2000 and there duly assigned Ser. No. 8225/2000.
1. Field of the Invention
The present invention relates to a back lighting apparatus of a liquid crystal display (LCD), and in particular to a back lighting apparatus of an LCD for implementing a three-dimensional image.
2. Description of the Background Art
Generally, in a liquid crystal display (LCD) apparatus, a voltage is applied to a liquid crystal which is an organic liquid formed of long chain molecules and which is in a semi-crystal liquid state based on a rearrangement of the molecules. Upon application of a voltage, the molecular structure is changed, thereby yielding a different light transmittance. A liquid crystal is filled into a gap formed between two thin glass plates, and a voltage is applied through a transparent electrode, so that the molecular structure of the liquid crystal is changed. Light penetrates through the liquid crystal from the back of the system. The above-described liquid crystal display has a slow response speed but consumes little power. In addition, it is possible to fabricate a thin plate-shaped liquid crystal display. Therefore, liquid crystal displays are increasingly being used in display apparatus of computers, in particular as the monitors of the computers.
The resolution of a liquid crystal display apparatus is determined based on a size and density of pixels of the apparatus, of the aperture ratio, field of view, light efficiency, etc.
The size and density of the pixels refers to a division of a liquid crystal display panel and affects the resolution of the screen. That is, in the liquid crystal display apparatus, as the size of the pixel is made smaller and the density of the pixels is increased, since the light which is transmitted by the liquid crystal display panel is divided more finely, the resolution is increased.
The aperture represents a ratio representing the fraction that the pixels actually occupy in the liquid crystal display panel and is a factor capable of determining the amount of light which is transmitted by each pixel of the liquid crystal display. Therefore, as the aperture is increased, the liquid crystal display apparatus consumes less power. However, in an actual liquid crystal display apparatus, there is a connection cable capable of supplying a pixel-based driving signal to the liquid crystal display panel. Therefore, it is impossible to obtain 100% aperture. In this case, the optical efficiency is increased based on a method of concentrating light at the pixels of the liquid crystal display panel.
The field of view represents an angle at which the information displayed on the flat-type display apparatus is correctly viewed in the front direction and is determined by a scattering angle of light which is transmitted the liquid crystal display panel.
The light efficiency represents a degree that the light generated in the back portion is transmitted by a liquid crystal display panel and is related to the aperture. The light efficiency can affect the power consumption of the liquid crystal display. That is, as the light efficiency increases, the liquid crystal display apparatus consumes less power.
Since the liquid crystal display does not itself generate light, the liquid crystal display includes a rear-direction lighting apparatus capable of generating light in the back portion, with the light being transmitted through the liquid crystal display.
In a conventional liquid crystal display apparatus and lighting method, a back lighting apparatus includes a light source, a light guide plate uniformly distributing light from the light source on the back of a liquid crystal display panel, prism plates for concentrating light incident from through the light guide plate, and a plurality of diffuser sheets for diffusing light concentrated by the prism plates onto the back surface of the liquid crystal display panel.
The back lighting apparatus of the conventional liquid crystal display apparatus uniformly distributes light onto the back surface of the liquid crystal display panel in the following ways.
The light from the light source is reflected from a reflection mirror which surrounds the light source or is directly inputted into the light guide plate from the light source. A part of the light inputted into the light guide plate is directly transmitted by a portion near the light source of an upper surface of the light guide plate and is transmitted by the prism plates. The remaining part is fully or partly reflected in the direction of a slanted lower surface of the light guide plate. The light among the light reflected by the upper surface is re-reflected in the direction of a portion slanted opposite to the light source, and a part of the light is scattered by a scattering portion of the lower surface and transmits the upper surface and is inputted into the prism plates. A part of the light which is reflected by the lower surface and is re-inputted into the upper surface directly transmits the upper surface and is inputted into the prism plates. The remaining light is reflected into the lower surface.
The light generated by the optical source is inputted into the light guide plate and is reflected by the horizontal upper surface and the slanted lower surface of the light guide plate and transmits in the direction opposite to the light source in the light guide plate and is inputted into the prism plate arranged parallel with a triangle prism and the prism plate parallel with the prism plate through the upper surface of the light guide plate. At this time, as the light is distanced from the light source, the distance of the light guide plate is decreased, and the scattering portion is distanced from the light source, a large amount of the light is scattered in a direction that the intensity of the light is relatively small.
Therefore, the light is uniformly inputted into the prism plate irrespective of the distance of the light source. In addition, the light is inputted near the vertical axis by the prism plates and and is transmitted by the film type diffuser sheets formed of small glass balls and is uniformly diffused and is inputted into the entire back surface of the liquid crystal display panel.
The back lighting apparatus of the conventional liquid crystal display apparatus is capable of uniformly distributing the light from the light source onto the back of the liquid crystal display panel. The back lighting apparatus of the conventional liquid crystal display apparatus includes the light source which is concentrated at a portion of the liquid crystal display panel, and the scattering portion is densely arranged for thereby scattering a large amount of the light. However, since the luminous intensity of the liquid crystal display panel is relatively weak at a portion distanced from the light source, it is impossible to uniformly output the light onto the liquid crystal display panel. Therefore, the liquid crystal display panel which uses the back lighting apparatus of the conventional liquid crystal display apparatus is not capable of obtaining a uniform resolution.
In addition, since the back lighting apparatus of the conventional liquid crystal display apparatus outputs light onto the entire portions of the liquid crystal display panel using one light source, the optical efficiency is decreased, and the power consumption is increased.
An LCD apparatus related to the above-described conventional apparatus is disclosed in U.S. Pat. No. 5,754,159, to Wood et al., entitled INTEGRATED LIQUID CRYSTAL DISPLAY AND BACKLIGHT SYSTEM FOR AN ELECTRONIC APPARATUS. In this patent, a stripe-shaped light source having a length slightly longer than the pixel line of the LCD panel is arranged in parallel, so that it is possible to obtain uniform light, and the light efficiency is high. However, it is difficult to fabricate the stripe-shaped light source, and the reliability of the product is decreased.
Another LCD apparatus related to the above-described conventional apparatus is disclosed in U.S. Pat. No. 5,748,828, to Steiner et al., entitled COLOR SEPARATING BACKLIGHT, which adapts a well known lighting method which is generally used by the known LCD apparatuses. However, the back lighting is too thick, and the light efficiency is decreased.
Additional lighting apparatus of the conventional art are seen in the following U.S. Patents.
U.S. Pat. No. 5,042,892, to Chiu et al., entitled FIBER OPTIC LIGHT PANEL, describes a light emitting panel formed by a single layer of parallel optical fibers. The fibers may have cladding removed on one side to allow light to escape.
U.S. Pat. No. 5,165,187, to Shahidi-Hamedani et al., entitled EDGE ILLUMINATED SIGN PANEL, describes an edge illuminated sign panel, which includes a flat ribbon of parallel optical fibers. The fibers leaving the ribbon are bundled and aligned to receive a light beam. Indicia may be formed by selectively abrading or embossing the surface of the ribbon to form areas from which the light may escape.
U.S. Pat. No. 5,187,765, to Muehlemann et al., entitled BACKLIGHTING PANEL, describes a light emitting panel backlighted by an optical fiber assembly in which the optical fibers are positioned in parallel across the bottom of a frame and transverse notches are scored into the cladding of the fibers to permit light emission.
U.S. Pat. No. 5,226,105, to Myers, entitled FIBER OPTIC BACKLIGHTING PANEL AND DOT PROCESS FOR MAKING SAME, describes a fiber optic backlighting panel having a layer of optical fibers arranged adjacent to each other. The optical fibers are selectively terminated at different locations using a laser.
U.S. Pat. No. 5,432,876, to Appeldom et al., entitled ILLUMINATION DEVICES AND OPTICAL FIBERS FOR USE THEREIN, describes an illumination device having a substantially parallel array of optical fibers and a front panel which is a liquid crystal shutter array. In this device, one fiber of every three transmits red light, one fiber transmits green light and one transmits blue light, to define a pixel. The fibers have notches of a variety of shapes to divert a proportion of the light propagating through the fiber to emit light from the fiber.
U.S. Pat. No. 5,542,016, to Kaschke, entitled OPTICAL FIBER LIGHT EMITTING APPARATUS, describes as conventional an optical fiber light emitting panel formed of a plurality of optical fibers arranged in parallel. The patent notes that disrupting the surface of an optical fiber by scratching at discrete locations leads to the emission of light at these locations.
U.S. Pat. No. 5,793,911, to Foley, entitled ILLUMINATION DEVICE, describes an illumination device for backlighting a liquid crystal display which includes a substrate containing a groove and an optical fiber fitted into the groove. The outer cladding layer of the optical fiber is of reduced thickness on the exposed side, leading to light emission through the reduced thickness layer.
U.S. Pat. No. 6,104,371, to Wang et al., entitled MODULAR HIGH-INTENSITY FIBER OPTIC BACKLIGHT FOR COLOR DISPLAYS, describes a modular fiber optic color backlight. The backlight uses polymer optical fiber having cut and refilled regions containing internal mirrors, which serve as taps for light to exit the fiber.
Moreover, in order to implement a three-dimensional image in a conventional LCD apparatus using backlighting, additional apparatus such as a lenticular, a parallax barrier, a polarization stripe plate, etc., is used for separating pixels at a plurality of points arranged by each pixel line of the LCD panel by spatial multiplexing. As such, the construction and structure are complicated. In addition, fabrication costs of such apparatus are increased.
It is therefore an object of the invention to provide a better liquid crystal display apparatus.
A further object of the invention is to provide a backlighting apparatus of a liquid crystal display.
A yet further object of the invention is to provide a liquid crystal display apparatus which can display a three-dimensional image.
A still further object of the invention is to provide a liquid crystal display apparatus which is simple in structure.
Another object of the invention is to provide a liquid crystal display apparatus which is optically efficient and consumes little power.
Accordingly, the present invention provides a back lighting apparatus of a liquid crystal display apparatus using an optical fiber capable of uniformly lighting the entire LCD apparatus by effectively supplying light to each pixel line of an LCD panel using the optical fiber, consuming a small amount of power based on a high optical efficiency and implementing a 3D image without using an additional apparatus.
To achieve the above objects, there is provided a back lighting apparatus of an LCD apparatus which includes a light source for generating light, a plurality of optical fibers having both ends optically connected with the light source and a part of the same attached to the back surface of the LCD panel for emitting the light generated by the light source to each pixel line of the LCD panel based on a scattering of the diffusion line for thereby lighting the entire portion of the back surface of the LCD panel, a support plate for fixing the optical fibers to the back surface of the LCD panel, and an optical diffusing unit for optically connecting the light source and the optical fibers.
Each optical fiber may include two diffusion lines capable of scattering light in different directions for thereby concurrently lighting two neighboring pixel lines.
A fresnel lens is attached on a front surface of the LCD panel for converging two scattering light which are scattered by two diffusion lines and transmit the pixel lines of the LCD panel at both sides of the front portion of the LCD panel for thereby implementing a 3D image.
The light scattering unit is surrounded by a reflection unit and includes both ends of each of the optical fibers, so that the light generated by the light source is scattered into air bubbles formed in the interior and converged into each optical fiber.